1. Field of the Invention
The present invention is directed to a system and method for saving power, and more specifically to a method and system for use with IEEE 802.11 compliant Media Access Controller (MAC) circuitry that enables and disables the main clock in coordination with 802.11 protocols and is also compliant with the Advanced Configuration and Power Interface (ACPI) power management and configuration interface specification.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Increasingly, electronic circuit manufacturers need to reduce the power consumption of their boards. The conservation of power is particularly important in portable electronic devices, such as wireless networking adapters or wireless phones where the product is specifically designed for use in situations where power outlets are not available. Wireless products usually must operate using internal batteries or rechargeable battery packs for extended periods of time, thus the conservation of battery power becomes a primary concern.
802.11 WLAN cards are often implemented as PCI and Cardbus cards. The MAC is required to be responsive to the host bus interface (PCI Bus) and events from a wireless or RF interface. The RF interface often utilizes IEEE 802.11 power management whereas the PCI Bus interface utilizes ACPI power management. Typically, a sleep timer is used to save power. The MAC goes into a sleep mode and the host processor can bring the MAC out of sleep by accessing the Card Information Structure (CIS) table and accessing certain host interface registers such as the command register. Once awakened, the MAC may decide that an action is required in response to the host interface wakeup or it may decide to resume its sleep mode. However, a clock is required to access and retrieve data from the CIS table, PCI configuration space and VPD data, and to issue commands to the MAC. Thus operating in a power save mode wherein the clock is disabled in sleep mode is problematic.
The IEEE 802.11 protocol specifies a procedure for mobile nodes to operate in a power saving mode. The mobile node may be in one of two states, awake and able to receive frames at any time, or power save (PS) wherein the mobile node is unable to transmit or receive and consumes very low power. The mobile node operating in power save mode is required to periodically return to an awake state to listen for traffic indication map (TIM) beacons which identify the mobile units for which traffic is pending and buffered at the AP. In addition, the TIM contains an indication whether broadcast/multicast traffic is pending. If the TIM beacon indicates traffic is pending for the mobile unit, the mobile unit must then stay awake until it has handled all its traffic and can then return to PS mode. Otherwise, if the TIM indicates that there is no traffic for the mobile node, the mobile node can immediately return to PS mode.
Finally, the Mini PCI and Cardbus specifications contain a mechanism that allows an opportunistic disabling of the PCI clock. When the PCI clock is active, it forces all devices on the bus segment to clock and use power. The PCI CLKRUN# mechanism allows a device to indicate to the bus that it will allow the clock to be disabled.
Thus the need exists for a method and system for use by a MAC for power management that is compatible with both IEEE 802.11 standards and the ACPI specification.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of instrumentalities and combinations particularly pointed out in the appended claims.